1. Field of the Invention
The present invention relates generally to indicating methods and apparatus, and more particularly to real-time, virtual image display apparatus for indicating the location of and distance to objects within a predetermined distance from a specified location. The invention specifically relates to a helmet or screen display for demonstrating to an aircraft pilot the relative locations of objects within a predetermined radius of a reference point in the pilot's airspace.
2. Background of the Invention
Head up displays have long been used in the military aircraft industry in combat exercises as well as in simulated, training exercises. Today, new areas of use are envisioned, as for example in space exploration, laporoscopic surgery, undersea operations, and hazardous waste clean-up activities.
Typically, when virtual image display equipment is used, the operator must analyze visual images depicting the spatial layout of his or her working environment, and in the course of doing so, may experience disorientation or uncertainty regarding his or her position within the depicted environment relative to some reference coordinate system or to other elements in the same environment.
There is therefore a need for apparatus which will enable operators to orient themselves and navigate within their working environement.
From U.S. Pat. No. 4,977,401 to Sjoberg, an aircraft display system is known which uses an inertial navigation platform 5, a signal processing unit 6, a picture producer or display generator 7 to detect and process signals, a cathode ray tube 8 and a mirror 9 to project an indicating display in the form of the inside of a sphere on a display comprised of a transparent reflecting plate known as a "combiner glass" 10. The aircraft pilot sees the indicator picture or display in a display plane 12 located at a certain distance from the pilot. A symbol 13 of the velocity vector of the aircraft and a symbol 14 of the x-axis of the aircraft are projected onto the display plane 12.
This apparatus, however, has proven to have several drawbacks. One is that it is forward-looking having a narrow field of view. For this reason, the pilot cannot ascertain the presence or position of moving objects outside of his present field of view. Another is that the presentation of spacial reference information spans across the entire reference field and therefore clutters and interferes with other images that the pilot may try to view simultaneously, such as target and weapon information, aircraft status, etc.